The heat generated in internal combustion engines for vehicles is utilized in part to heat, by way of the hot exhaust gas, an exhaust-gas purification apparatus to an operating temperature required for the operation of the exhaust-gas purification apparatus. With progressive operating duration and increasing operating intensity, that is to say high power output of the internal combustion engine, the exhaust-gas purification apparatus is however heated further, such that, above a defined temperature, cooling of the exhaust-gas purification apparatus is necessary. Owing to the high temperatures, however, cooling is not possible by means of a simple cooling circuit which contains a coolant or water vapor, for example because coolants are not designed for such high temperatures.
It is an object of the invention to provide an engine assembly which permits effective cooling of the exhaust-gas purification apparatus and improved utilization of the heat generated by the engine.
To achieve the object, it is provided, in the case of an engine assembly of the type mentioned in the introduction, that the flow transfer line is led at least in sections through the exhaust-gas purification apparatus, wherein an exchange of heat takes place between the exhaust-gas purification apparatus and the gas flowing in the flow transfer line. The heat engine functions on the basis of the principle of a Stirling engine, wherein, during a movement of the at least one piston, the gas flows through the flow transfer line between the heating region and the cooling region. The flow transfer line that is led through the exhaust-gas purification apparatus functions, in effect, as a heat exchanger. The gas flowing through the flow transfer line can thus absorb heat from the exhaust-gas purification apparatus or release heat to the latter. Upon starting of the internal combustion engine, it is thus possible for the exhaust-gas purification apparatus to be heated up more quickly, for example by way of a release of heat, such that said exhaust-gas purification apparatus reaches its operating temperature more quickly. When the exhaust-gas purification apparatus has reached its operating temperature, the gas can absorb excess heat and conduct it away from the exhaust-gas purification apparatus, that is to say cool the exhaust-gas purification apparatus and thus prevent or at least delay an increase in temperature of the exhaust-gas purification apparatus. This type of cooling by means of a Stirling engine offers the advantage that a heat engine of said type can be operated even at very high temperatures.
The heating device for the heat engine or the first end section of the working chamber for the heat engine may be formed for example by the internal combustion engine and/or the exhaust-gas purification apparatus. The heat of the internal combustion engine and/or of the exhaust-gas purification apparatus can thus be utilized in an effective manner, and no additional energy source for the heat engine is required. Energy-saving cooling of the exhaust-gas purification apparatus is thus realized.
The flow transfer line may for example branch within the exhaust-gas purification apparatus into multiple sub-lines, such that, owing to the larger surface area between the exhaust-gas purification apparatus and flow transfer line, a significantly improved exchange of heat is possible between the exhaust-gas purification apparatus and the gas flowing through the flow transfer line.
The flow transfer line or the sub-lines may be led through the exhaust-gas purification apparatus in any desired manner in order to realize the best possible exchange of heat between the flow transfer line or sub-lines and exhaust-gas purification apparatus. The flow transfer line or the sub-lines are preferably led through the exhaust-gas purification apparatus in a flow direction, such that an exchange of heat is possible over as great a distance as possible.
The gas may for example flow from the heating region into the cooling region through the flow transfer line in the flow direction of the exhaust-gas purification apparatus.
It is however also conceivable for the gas to flow from the heating region into the cooling region through the flow transfer line counter to the flow direction of the exhaust-gas purification apparatus, whereby an improved exchange of heat or an improved dissipation of heat from the exhaust-gas purification apparatus is possible.
It is however optionally also conceivable for the flow transfer line or sub-lines of the flow transfer line to be led through the exhaust-gas purification apparatus substantially transversely with respect to the flow direction of the exhaust-gas purification apparatus.
In a first embodiment, the heating device is assigned to the first cylinder and the cooling device is assigned to the second cylinder. The heating region is provided in the first cylinder, and the cooling region is provided in the second cylinder. This construction corresponds to a conventional Stirling engine with a working piston and a displacement piston, wherein, depending on the construction of the Stirling engine, the first or the second piston constitutes the working piston, and the respective other piston constitutes the displacement piston.
The first and/or the second piston are/is for example of magnetic form, and an electrical coil is provided which circumferentially surrounds the first and/or the second cylinder between the initial position and expansion position. When the piston moves in the working chamber, this causes an electrical induction current to be generated in the coil, such that electrical current can be generated by way of the mechanical work of the piston.
In a second embodiment, a first heating region, a first cooling region and a first flow transfer line which connects the first heating region and the first cooling region to one another in terms of flow are provided on the first cylinder, and a second heating region, a second cooling region and a second flow transfer line which connects the second heating region and the second cooling region to one another in terms of flow are provided on the second cylinder, wherein the flow transfer lines are each arranged such that a connection in terms of flow is produced between the heating region and the cooling region only in the expansion position of the pistons. In particular, the first and the second cylinder are arranged one behind the other in the longitudinal direction, and the cooling regions or the heating regions are adjacent to one another. In this embodiment, in effect, two Stirling engines are integrated into one another, wherein the working piston and the displacement piston of the first Stirling engine form the displacement piston and the working piston of the second Stirling engine. This construction offers the advantage that only one common cooling device or heating device is required for the mutually adjacent cooling regions or heating regions, whereby improved utilization of the cooling power or heating power is possible. In this embodiment, the first cylinder together with the first flow transfer line form a first, closed working chamber, and the second cylinder together with the second flow transfer line form a second working chamber which is separate from the first working chamber.
In this embodiment, too, the pistons may be of magnetic form. On at least one cylinder, there is provided an electrical coil which circumferentially surrounds the first and/or the second cylinder between the initial position and expansion position. In this embodiment, the pistons may additionally be oriented such that the magnetic fields of the pistons repel one another. This additionally offers the advantage that the pistons are coupled by way of the magnetic fields, such that one of the pistons, which is moved toward the connecting region of the two cylinders, repels the respective other piston.
Further advantages and features will emerge from the following description in conjunction with the appended drawings, in which:
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.